Excess placental soluble fms-like tyrosine kinase 1 (sFlt1) may contribute to endothelial dysfunction, hypertension, and proteinuria in preeclampsia

TLDR

Preeclampsia affects about 5 % of pregnancies, causing significant maternal and fetal morbidity, yet its pathophysiology is largely unknown, with a prevailing hypothesis that placental ischemia triggers soluble factors that induce endothelial dysfunction leading to hypertension, proteinuria, and edema. Placental ischemia is thought to initiate production of soluble factors that cause maternal endothelial dysfunction. We found that sFlt1 is markedly elevated in preeclampsia, correlates with reduced free VEGF and PlGF, induces endothelial dysfunction in vitro that is reversible with VEGF/PlGF, and when administered to pregnant rats causes hypertension, proteinuria, and glomerular endotheliosis, supporting a causal role for excess sFlt1 in preeclampsia.

Abstract

Preeclampsia, a syndrome affecting 5% of pregnancies, causes substantial maternal and fetal morbidity and mortality. The pathophysiology of preeclampsia remains largely unknown. It has been hypothesized that placental ischemia is an early event, leading to placental production of a soluble factor or factors that cause maternal endothelial dysfunction, resulting in the clinical findings of hypertension, proteinuria, and edema. Here, we confirm that placental soluble fms-like tyrosine kinase 1 (sFlt1), an antagonist of VEGF and placental growth factor (PlGF), is upregulated in preeclampsia, leading to increased systemic levels of sFlt1 that fall after delivery. We demonstrate that increased circulating sFlt1 in patients with preeclampsia is associated with decreased circulating levels of free VEGF and PlGF, resulting in endothelial dysfunction in vitro that can be rescued by exogenous VEGF and PlGF. Additionally, VEGF and PlGF cause microvascular relaxation of rat renal arterioles in vitro that is blocked by sFlt1. Finally, administration of sFlt1 to pregnant rats induces hypertension, proteinuria, and glomerular endotheliosis, the classic lesion of preeclampsia. These observations suggest that excess circulating sFlt1 contributes to the pathogenesis of preeclampsia.